Vdiscussion » Uncategorized http://vdiscussion.com Vinoth Kumar's Discussion Wed, 09 Dec 2009 15:34:03 +0000 en hourly 1 Explain about Database Concurrency Issues http://vdiscussion.com/explain-about-database-concurrency-issues/ http://vdiscussion.com/explain-about-database-concurrency-issues/#comments Mon, 16 Nov 2009 14:27:38 +0000 ma.vinothkumar http://vdiscussion.com/?p=85 When multiple users try to update a single record at the same time, you will have concurrency issues. In a single-tier application, this is never an issue because there is only one user accessing data. In a two-tier system, you as the developer have the option of implementing either pessimistic or optimistic locking—however, this depends on the Relational Database Management System (RDBMS) because not all databases support optimistic locking. In most two-tier applications, you are always connected to the database when you are reading and writing data. If you set up pessimistic concurrency, when one user is trying to update a record, no other user can update the record at the same time (they will receive an error message explaining that the record is locked). If you implement optimistic concurrency, you will have to write code to handle the occurrence of one user updating a record that is not current. In a three-tier application, the developer must always handle database updates because no connection is maintained with the database. In most cases, this applies to a well-written two-tier application as well.

Microsoft’s new database access technology, ADO.NET, can help to make many of these issues easier to solve—but even ADO.NET will only throw an exception saying that someone else has updated the record. It is still up to the developer to handle this situation, and it is rarely solved the same way on any two applications. How you handle this situation depends mostly on what the users want.

]]> http://vdiscussion.com/explain-about-database-concurrency-issues/feed/ 0 What is XML ? http://vdiscussion.com/what-is-xml/ http://vdiscussion.com/what-is-xml/#comments Thu, 12 Nov 2009 12:24:37 +0000 ma.vinothkumar http://vdiscussion.com/?p=42 XML stands for Extensible Markup Language, was defined by the
XML Working Group of the World Wide Web Consortium (W3C). This group
described the language as follows:
The Extensible Markup Language (XML) is a subset of SGML…Its
goal is to enable generic SGML to be served, received, and processed
on the Web in the way that is now possible with HTML. XML has been
designed for ease of implementation and for interoperability with both
SGML and HTML.

As you can see, XML is a markup language designed specifically for delivering
information over the World Wide Web, just like HTML (Hypertext Markup
Language), which has been the standard language used to create Web pages
since the inception of the Web. Since we already have HTML, which continues
to evolve to meet additional needs, you might wonder why we require a com-
pletely new language for the Web.

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